scholarly journals MoS2-Carbon Inter-overlapped Structures as Effective Electrocatalysts for the Hydrogen Evolution Reaction

Nanomaterials ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 1389
Author(s):  
Po-Chia Huang ◽  
Chia-Ling Wu ◽  
Sanjaya Brahma ◽  
Muhammad Omar Shaikh ◽  
Jow-Lay Huang ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Photoelectron Spectroscopy ◽  
Active Sites ◽  
Hydrogen Generation ◽  
Interlayer Spacing ◽  
Monolayer Mos2 ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron

The ability to generate hydrogen in an economic and sustainable manner is critical to the realization of a future hydrogen economy. Electrocatalytic water splitting into molecular hydrogen using the hydrogen evolution reaction (HER) provides a viable option for hydrogen generation. Consequently, advanced non-precious metal based electrocatalysts that promote HER and reduce the overpotential are being widely researched. Here, we report on the development of MoS2-carbon inter-overlapped structures and their applicability for enhancing electrocatalytic HER. These structures were synthesized by a facile hot-injection method using ammonium tetrathiomolybdate ((NH4)2MoS4) as the precursor and oleylamine (OLA) as the solvent, followed by a carbonization step. During the synthesis protocol, OLA not only plays the role of a reacting solvent but also acts as an intercalating agent which enlarges the interlayer spacing of MoS2 to form OLA-protected monolayer MoS2. After the carbonization step, the crystallinity improves substantially, and OLA can be completely converted into carbon, thus forming an inter-overlapped superstructure, as characterized in detail using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). A Tafel slope of 118 mV/dec is obtained for the monolayer MoS2-carbon superstructure, which shows a significant improvement, as compared to the 202 mV/dec observed for OLA-protected monolayer MoS2. The enhanced HER performance is attributed to the improved conductivity along the c-axis due to the presence of carbon and the abundance of active sites due to the interlayer expansion of the monolayer MoS2 by OLA.

scholarly journals Amorphous Ni x Co y P-supported TiO2 nanotube arrays as an efficient hydrogen evolution reaction electrocatalyst in acidic solution

2019 ◽  
Vol 10 ◽  
pp. 62-70 ◽  
Author(s):  
Yong Li ◽  
Peng Yang ◽  
Bin Wang ◽  
Zhongqing Liu
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Photoelectron Spectroscopy ◽  
Electrochemical Impedance ◽  
Nanotube Arrays ◽  
Active Surface Area ◽  
X Ray ◽  
Transmission Electron

Bimetallic phosphides have been attracting increasing attention due to their synergistic effect for improving the hydrogen evolution reaction as compared to monometallic phosphides. In this work, NiCoP modified hybrid electrodes were fabricated by a one-step electrodeposition process with TiO2 nanotube arrays (TNAs) as a carrier. X-ray diffraction, transmission electron microscopy, UV–vis diffuse reflection spectroscopy, X-ray photoelectron spectroscopy and scanning transmission electron microscopy/energy-dispersive X-ray spectroscopy were used to characterize the physiochemical properties of the samples. The electrochemical performance was investigated by cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy. We show that after incorporating Co into Ni–P, the resulting Ni x Co y P/TNAs present enhanced electrocatalytic activity due to the improved electron transfer and increased electrochemically active surface area (ECSA). In 0.5 mol L−1 H2SO4 electrolyte, the Ni x Co y P/TNAs (x = 3.84, y = 0.78) demonstrated an ECSA value of 52.1 mF cm−2, which is 3.8 times that of Ni–P/TNAs (13.7 mF cm−2). In a two-electrode system with a Pt sheet as the anode, the Ni x Co y P/TNAs presented a bath voltage of 1.92 V at 100 mA cm−2, which is an improvment of 79% over that of 1.07 V at 10 mA cm−2.

scholarly journals Electrochemical Hydrogen Evolution over Hydrothermally Synthesized Re-Doped MoS2 Flower-Like Microspheres

Molecules ◽  
2019 ◽  
Vol 24 (24) ◽  
pp. 4631 ◽  
Author(s):  
Juan Aliaga ◽  
Pablo Vera ◽  
Juan Araya ◽  
Luis Ballesteros ◽  
Julio Urzúa ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Hydrogen Evolution ◽  
Photoelectron Spectroscopy ◽  
Charge Transfer Resistance ◽  
Chemical Analyses ◽  
X Ray Diffraction ◽  
Transfer Resistance ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Electron

In this research, we report a simple hydrothermal synthesis to prepare rhenium (Re)- doped MoS2 flower-like microspheres and the tuning of their structural, electronic, and electrocatalytic properties by modulating the insertion of Re. The obtained compounds were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Structural, morphological, and chemical analyses confirmed the synthesis of poorly crystalline Re-doped MoS2 flower-like microspheres composed of few stacked layers. They exhibit enhanced hydrogen evolution reaction (HER) performance with low overpotential of 210 mV at current density of 10 mA/cm2, with a small Tafel slope of 78 mV/dec. The enhanced catalytic HER performance can be ascribed to activation of MoS2 basal planes and by reduction in charge transfer resistance during HER upon doping.

scholarly journals A Facile and Waste-Free Strategy to Fabricate Pt-C/TiO2Microspheres: Enhanced Photocatalytic Performance for Hydrogen Evolution

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Hui Li ◽  
Xiaoyan Zhang ◽  
Xiaoli Cui
Keyword(s):  
Hydrogen Evolution ◽  
Photoelectron Spectroscopy ◽  
Hydrogen Generation ◽  
Synthesis Method ◽  
Diffraction Field ◽  
Light Illumination ◽  
Thermal Synthesis ◽  
X Ray ◽  
Photocatalytic Hydrogen Generation ◽  
Transmission Electron

A facile and waste-free flame thermal synthesis method was developed for preparing Pt modified C/TiO2microspheres (Pt-C/TiO2). The photocatalysts were characterized with X-ray diffraction, field emission scanning electron microscopy, transmission electron microscope, ultraviolet-visible (UV-vis) diffuse reflectance spectra, X-ray photoelectron spectroscopy, and thermogravimetry analysis. The photocatalytic activity was evaluated by hydrogen evolution from water splitting under UV-vis light illumination. Benefitting from the electron-hole separation behavior and reduced overpotential of H+/H2, remarkably enhanced hydrogen production was demonstrated and the photocatalytic hydrogen generation from 0.4 wt% Pt-C/TiO2increased by 22 times. This study also demonstrates that the novel and facile method is highly attractive, due to its easy operation, requiring no post treatment and energy-saving features.

scholarly journals Comparative Study of the Photocatalytic Hydrogen Evolution over Cd1−xMnxS and CdS-β-Mn3O4-MnOOH Photocatalysts under Visible Light

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 355
Author(s):  
Ksenia O. Potapenko ◽  
Anna Yu. Kurenkova ◽  
Andrey V. Bukhtiyarov ◽  
Evgeny Yu. Gerasimov ◽  
Svetlana V. Cherepanova ◽  
...  
Keyword(s):  
Solid Solution ◽  
Visible Light ◽  
Hydrogen Evolution ◽  
Photoelectron Spectroscopy ◽  
Diffuse Reflectance Spectroscopy ◽  
Diffraction Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Manganese Salts

A series of solid solutions of cadmium and manganese sulfides, Cd1−xMnxS (x = 0–0.35), and composite photocatalysts, CdS-β-Mn3O4-MnOOH, were synthesized by precipitation with sodium sulfide from soluble cadmium and manganese salts with further hydrothermal treatment at 120 °C. The obtained photocatalysts were studied by the X-ray diffraction method (XRD), UV-vis diffuse reflectance spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and N2 low temperature adsorption. The photocatalysts were tested in hydrogen production using a Na2S/Na2SO3 aqueous solution under visible light (λ = 450 nm). It was shown for the first time that both kinds of photocatalysts possess high activity in hydrogen evolution under visible light. The solid solution Cd0.65Mn0.35S has an enhanced photocatalytic activity due to its valence and conduction band position tuning, whereas the CdS-β-Mn3O4-MnOOH (40–60 at% Mn) samples were active due to ternary heterojunction formation. Further, the composite CdS-β-Mn3O4-MnOOH photocatalyst had much higher stability in comparison to the Cd0.65Mn0.35S solid solution. The highest activity was 600 mmol g−1 h−1, and apparent quantum efficiency of 2.9% (λ = 450 nm) was possessed by the sample of CdS-β-Mn3O4-MnOOH (40 at% Mn).

Electrodeposited Co–Zn on Ni foam as efficient catalysts for hydrogen generation from hydrolysis of sodium borohydride

2017 ◽  
Vol 10 (05) ◽  
pp. 1750065 ◽  
Author(s):  
Lei Wei ◽  
Maixia Ma ◽  
Yanhong Lu ◽  
Suling Zhang ◽  
Jing Gao ◽  
...  
Keyword(s):  
Sodium Borohydride ◽  
Photoelectron Spectroscopy ◽  
Active Sites ◽  
Hydrogen Generation ◽  
Energy Dispersive Spectrometer ◽  
X Ray Diffraction ◽  
Water Displacement ◽  
Ni Foam ◽  
X Ray ◽  
Naoh Solution

For hydrogen generation based on the sodium borohydride hydrolysis, the development and application of efficient catalysts are of key importance. In this work, Co and Co–Zn catalysts were prepared on Ni foam by electrodeposition process. Field-emission scanning electron microscopy (FE-SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were employed for materials characterization, and catalyst performance was measured by typical water-displacement method. Experimental results indicate that the doping of zinc affects the morphology and microstructure of catalyst and promotes the effective catalytic area, leading to higher hydrogen generation rate (HGR) by comparing with Co/Ni. Furthermore, HGR can be further improved by treating the Co–Zn/Ni with NaOH solution because the partial dissolving of zinc results in the increase of cobalt active sites. Using a 10[Formula: see text]wt.% NaBH4 and 5[Formula: see text]wt.% NaOH solution, the HGR was as high as 455[Formula: see text]mL min[Formula: see text] g[Formula: see text] at 25[Formula: see text]C, and the apparent activation energy was measured to be 50.2[Formula: see text]kJ mol[Formula: see text]. Cyclic performance of the NaOH-treated Co–Zn/Ni was investigated as well.

Synthesis of the rod-like NiS2@C for hydrogen evolution reaction in acidic solution

2020 ◽  
Vol 13 (02) ◽  
pp. 2050009
Author(s):  
Xiujuan Wu ◽  
Jie Wang ◽  
Fan Zhang ◽  
Junyan Gong ◽  
Pinghao Xu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Hydrogen Evolution ◽  
Photoelectron Spectroscopy ◽  
Acidic Solution ◽  
Carbon Film ◽  
Chemical Deposition ◽  
X Ray Diffraction ◽  
X Ray ◽  
Onset Potential ◽  
Transmission Electron

The carbon-based NiS2 nanorods (NiS2@C) were prepared by chemical deposition and sulfidation with nickel dimethylglyoximate (Ni(DMG)2) as the starting agent. The nanorods were analyzed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy for chemical analysis. Structural characterization revealed that NiS2 existed on the surface of the rod and in the internal channels of the rod. In 0.5[Formula: see text]m H2SO4 solution, NiS2@C has lower onset potential and higher current density than NiS2. The results suggest that C improves the electrical conductivity of the NiS2 electrocatalyst, and the carbon film-based rod-like NiS2 is a more effective nanocomposite of hydrogen evolution.

scholarly journals WS2–WC–WO3 nano-hollow spheres as an efficient and durable catalyst for hydrogen evolution reaction

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Tuan Van Nguyen ◽  
Ha Huu Do ◽  
Mahider Tekalgne ◽  
Quyet Van Le ◽  
Thang Phan Nguyen ◽  
...  
Keyword(s):  
Transition Metal ◽  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Transition Metal Oxides ◽  
Photoelectron Spectroscopy ◽  
Active Sites ◽  
Low Cost ◽  
Hollow Spheres ◽  
Efficient Catalyst ◽  
X Ray

AbstractTransition metal dichalcogenides (TMDs), transition metal carbides (TMCs), and transition metal oxides (TMOs) have been widely investigated for electrocatalytic applications owing to their abundant active sites, high stability, good conductivity, and various other fascinating properties. Therefore, the synthesis of composites of TMDs, TMCs, and TMOs is a new avenue for the preparation of efficient electrocatalysts. Herein, we propose a novel low-cost and facile method to prepare TMD–TMC–TMO nano-hollow spheres (WS2–WC–WO3 NH) as an efficient catalyst for the hydrogen evolution reaction (HER). The crystallinity, morphology, chemical bonding, and composition of the composite material were comprehensively investigated using X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, and X-ray photoelectron spectroscopy. The results confirmed the successful synthesis of the WS2–WC–WO3 NH spheres. Interestingly, the presence of nitrogen significantly enhanced the electrical conductivity of the hybrid material, facilitating electron transfer during the catalytic process. As a result, the WS2–WC–WO3 NH hybrid exhibited better HER performance than the pure WS2 nanoflowers, which can be attributed to the synergistic effect of the W–S, W–C, and W–O bonding in the composite. Remarkably, the Tafel slope of the WS2–WC–WO3 NH spheres was 59 mV dec−1, which is significantly lower than that of the pure WS2 NFs (82 mV dec−1). The results also confirmed the unprecedented stability and superior electrocatalytic performance of the WS2–WC–WO3 NH spheres toward the HER, which opens new avenues for the preparation of low-cost and highly effective materials for energy conversion and storage applications.

scholarly journals α-Cellulose Fibers of Paper-Waste Origin Surface-Modified with Fe3O4 and Thiolated-Chitosan for Efficacious Immobilization of Laccase

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 581
Author(s):  
Gajanan S. Ghodake ◽  
Surendra K. Shinde ◽  
Ganesh D. Saratale ◽  
Rijuta G. Saratale ◽  
Min Kim ◽  
...  
Keyword(s):  
Enzyme Immobilization ◽  
Photoelectron Spectroscopy ◽  
Cellulose Fibers ◽  
Relative Activity ◽  
Significant Activity ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Laccase Immobilization ◽  
Surface Modified

The utilization of waste-paper-biomass for extraction of important α-cellulose biopolymer, and modification of extracted α-cellulose for application in enzyme immobilization can be extremely vital for green circular bio-economy. Thus, in this study, α-cellulose fibers were super-magnetized (Fe3O4), grafted with chitosan (CTNs), and thiol (-SH) modified for laccase immobilization. The developed material was characterized by high-resolution transmission electron microscopy (HR-TEM), HR-TEM energy dispersive X-ray spectroscopy (HR-TEM-EDS), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR) analyses. Laccase immobilized on α-Cellulose-Fe3O4-CTNs (α-Cellulose-Fe3O4-CTNs-Laccase) gave significant activity recovery (99.16%) and laccase loading potential (169.36 mg/g). The α-Cellulose-Fe3O4-CTNs-Laccase displayed excellent stabilities for temperature, pH, and storage time. The α-Cellulose-Fe3O4-CTNs-Laccase applied in repeated cycles shown remarkable consistency of activity retention for 10 cycles. After the 10th cycle, α-Cellulose-Fe3O4-CTNs possessed 80.65% relative activity. Furthermore, α-Cellulose-Fe3O4-CTNs-Laccase shown excellent degradation of pharmaceutical contaminant sulfamethoxazole (SMX). The SMX degradation by α-Cellulose-Fe3O4-CTNs-Laccase was found optimum at incubation time (20 h), pH (3), temperatures (30 °C), and shaking conditions (200 rpm). Finally, α-Cellulose-Fe3O4-CTNs-Laccase gave repeated degradation of SMX. Thus, this study presents a novel, waste-derived, highly capable, and super-magnetic nanocomposite for enzyme immobilization applications.

scholarly journals Surface Stoichiometry and Depth Profile of Tix-CuyNz Thin Films Deposited by Magnetron Sputtering

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3191
Author(s):  
Arun Kumar Mukhopadhyay ◽  
Avishek Roy ◽  
Gourab Bhattacharjee ◽  
Sadhan Chandra Das ◽  
Abhijit Majumdar ◽  
...  
Keyword(s):  
Magnetron Sputtering ◽  
Photoelectron Spectroscopy ◽  
Film Surface ◽  
Grazing Incidence ◽  
X Ray Diffraction ◽  
X Ray ◽  
Relative Composition ◽  
Transmission Electron ◽  
Deposited Film ◽  
Deposited Films

We report the surface stoichiometry of Tix-CuyNz thin film as a function of film depth. Films are deposited by high power impulse (HiPIMS) and DC magnetron sputtering (DCMS). The composition of Ti, Cu, and N in the deposited film is investigated by X-ray photoelectron spectroscopy (XPS). At a larger depth, the relative composition of Cu and Ti in the film is increased compared to the surface. The amount of adventitious carbon which is present on the film surface strongly decreases with film depth. Deposited films also contain a significant amount of oxygen whose origin is not fully clear. Grazing incidence X-ray diffraction (GIXD) shows a Cu3N phase on the surface, while transmission electron microscopy (TEM) indicates a polycrystalline structure and the presence of a Ti3CuN phase.

scholarly journals Synthesis of Ce1−xPdxO2−δ Solid Solution in Molten Nitrate

Catalysts ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 640
Author(s):  
Hideaki Sasaki ◽  
Keisuke Sakamoto ◽  
Masami Mori ◽  
Tatsuaki Sakamoto
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
Solid Solutions ◽  
Photoelectron Spectroscopy ◽  
Synthesis Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Co Precipitation ◽  
Ionic States

CeO2-based solid solutions in which Pd partially substitutes for Ce attract considerable attention, owing to their high catalytic performances. In this study, the solid solution (Ce1−xPdxO2−δ) with a high Pd content (x ~ 0.2) was synthesized through co-precipitation under oxidative conditions using molten nitrate, and its structure and thermal decomposition were examined. The characteristics of the solid solution, such as the change in a lattice constant, inhibition of sintering, and ionic states, were examined using X-ray diffraction (XRD), scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM−EDS), transmission electron microscopy (TEM)−EDS, and X-ray photoelectron spectroscopy (XPS). The synthesis method proposed in this study appears suitable for the easy preparation of CeO2 solid solutions with a high Pd content.

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